Tread block core for endless tracks and the like



March 6, 1945- R. l. SCHONITZER TREAD BLOCK CORES FOR ENDLESS TRACKS ANDTHE LIKE Filed Jan. 14, 1942 10 Sheets-Sheet 1 /NVEN7OR RUDOLPH I.SCHONITZER 7 I aw! fizzy A'r'ronw'svs.

March 6, 1945. R SCHQNITZER 2,371,071

TREAD BLOCK CORE-3S FOR ENDLESS TRACKS AND THE LIKE Filed Jan. 14, 194210 Sheets-Sheet 2 //v VEN TOR RUDOLPH I. SCHONITZER m fi A T1- @g 9; 9 k2 a 0 T Q Mm i. 3x 11 m MW TOHNEYS.

March 6, 1945. R.l. SCHONITZER 2,371,071

TREAD BLOCK CORES FOR ENDLESS TRACKS AND THE LIKE Filed Jan. 14, 1942 10Sheets-Sheet s 101 (34101 /NVENTOR FIG 3 I RUDOLPH I. Scum/T253 BY %AMATTORNEYS.

March 6, 1945.

R. l. SCHONITZER TREAD BLOCK CORES FOR ENDLESS TRACKS AND THE LIKE FiledJan. 14, 1942 10 Sheets-Sheet 4 l a]? i l ,1! l 41 I iii a :2: 5 i=2 41V W 5 5H I l jg L as E i-i: l 4 k .14. iii: i III/I/II/ [III/Ill] '2 38I 2// /3 RUDOLPH I. Scuomvzm. /l'III/I/I/i Fez/2 M I Arron/v Ys.

March 6, 1945. R. SCHONITZER 2,371,071

TREAD BLOCK CURES FOR ENDLESS TRACKS AND THE LIKE Filed Jan. 14, 1942 10Sheets-Sheet 5 IIIIIIIIIIIIII IIIIII/IIIIIII/II/[I/I/ /N VENTOf? R0001.PH 1'. SCHON/TZER TTORNEYS.

March 6, 1945- R. l. SCHONITZER TREAD BLOCK CORES FOR ENDLESS TRACKS ANDTHE LIKE l0 Sheets-Sheet 6 Filed Jar}. -'l4, 1942 /N vE/v'roH RUDOLPH 1fSCHON/TZER TTORNEYS.

March 6, 1945- R. SCHONITZER TREAD BLOCK CORES FOR ENDLESS TRACKS ANDTHE LIKE Filed Jan. 14, 1942 10 Sheets-Sheet 7 vE/v Ton HUDOL PH I.scHozvn-zsn I 7 My A T TORNEYS.

FIG. 26

Mai-ch 6, 1945- R. 1. SCHONITZER TREAD BLOCK CORES FOR ENDLESS TRACKSAND THE LIKE 1o Sheets -Sheet 8 Filed Jan. 14, 1942 /NVENTOR RUDOLPH I.SCHON/TZER TTORNEYS March 6, 1945- R. l. SCHONITZER TREAD BLOCK CO RESFOR ENDLESS TRACKS AND THE'LIKE Filed Jan. 14, 1942 10 Sheets-Sheet 9Wm. m. mo 8 RUDOLPH I. SCHON/TZER A644, M AT-roR March 1945- R. l.SCHONITZER TREAD BLOCK CORES FOR ENDLESS TRACKS AND THE LIKE Filed Jan.14, 1942 10 Sheets-Sheet 1O l lllllll llllllll lll Illlllllll lll I l Il ll //v VEN Tan 5000/. PH I SCHONITZER FIG. 4/

B Y 7 M 7? zfromvs s.

Patented Mar. 6,1945

TREAD BLOCK CORE FOR ENDLESS TRACKS AND THE LIKE i Rudolph I;Schon'itzer, Shaker-Heights, Ohio Application J anuary-14, 1942, SerialNo.426,666

31 Claims. (01. s '1 0) This invention relates toendless tracks forvehicles such as tanks, tractors and the like.

More particularly, the present invention relates to improvements in there-enforcing cores forthe rubber tread blocks of such tracks.

The type of tread block core with which the present invention isconcerned is one having generally cylindrical passageways adjacent, andsubstantially parallel with the front and rear edges thereof, for theextension therethrough of cross rods by means, of which a, set of treadblocks,

containing cores of the-characterhere involved,

may be connected to form anendless track, the

laterally projecting end portions. of said cross rods being provided, oneach side. of the track,

with suitable means which not only maintain the tread blocks inassembled, track-forming relation but which also cooperate in thedriving and guiding ofthe track. Heretofore, it has been the practice toembed within the rubber-- of ,the tread blocks transverselydisposedseamless tubing, for the reception of the cross rods,-

and spacing strips for such tubing, a type of tread block core which-hasnot been satisfactory; a The present invention thereforehas for itsgeneral object the pIOViSiOII of novel and improved cores for the rubbertread blocks of endless tracks, the re-enforcing character of said coresenabling rubber tread blocks provided therewith to successfullywithstand the severeabuse to which such blocks are subjected in use inendless tracks, particularly the tread blocks of the endless tracks ofheavy armored tanks and the like. 7 v w A more specific object of thepresent invention is the provision of tread block cores which;

are made ofsimple and inexpensive sheet metal parts, portions of whichare constructed to provide cylindrical passageways through the treadblocks for the reception of the aforesaid cross rods, and which sheetmetal cores, although of mounted upon'or carried by the laterallyprojecting ends of the cross rods-which extend through the blocks ofsaid track being, omitted;

Fig.2 is a view, partly. invertical section and partly'in sideelevation, of the track section of Fig. 1, the-view being on'the line2--2, Fig. '1; Fig. 3 is a top plan view of the core. of one of;

the side tread blocks of the track of Figs. 1 and 2, the slightlyprojecting end portions of the two layers of rubber which are bonded tothe oppo-z site faces of said coreto form a tread block' beingindicated-in dot-dash lines;

Fig. 4 is a side elevational view'of saidcore; and showing in dot-dashlines the outer peripheriesof the two layers of; bonded thereto;

Fig. 5 is a cross sectional view of aside tread block containing thecore of Figs. 3 and 4, the," view being in the plane of the line5--5,,Fig. (it.

Fig. 6 is anexploded type of view, showing in sideelevationthree ofthefour sheet metal members which make up the core of Figs."3, gland 5,.

the fourth and other outer member of the. core; not shown in Fig. =6,being identical with the outer core member shown at the top of Fig. 6;;

7 Fig.1? is a top-plan. view of the outerjcore member shown in Fig. 6,as viewed from theline.

l--1 Fig. 6, the view also being illustrative of the other outer coremember not shown in Fig; 6;,

Fig, 8 is a top plan view of one .of. the two inner core members,as-viewed from the line 88, .Fig. 6. the view also being illustrativeof.

the other inner core members, inasmuch as the two inner'core members areidentical;

relatively light weight, have'surprisingly great strength, rigidity andruggedness for the efiective re-enforcement of therubber of the treadblocks.

Other objects of the present invention-will appear from the followingdescription of several tread block cores embodying said invention, ref:erence being had to the accompanying drawings, in which Fig. 1 is a topplan view of a section of one form of endless track having rubber treadblocks provided with cores embodying the presentin vention, the meanswhichco'nnect and which are Fig. 9isa cross sectional view of one ofthe;

outercore members, the view being on the line 9-9, Fig. 6; a

Fig. 10 is a view similar to Fig. 4, but showing a two piece core,whichmaybe usedjin either the side or the middle'tread blocks oi the track ofFigs. land 2;

Fig; ll-isa view similar to Figs. 4 and 10, but, i showing a modifiedform of two-piece core, which maybeusedin the side tread blocks ofthetrack of Figs. ;1 and 2;

Fig. 12 is a cross sectional view tread block containing the. core ofFig. 11,,the

view being in the plane of the line] 2l2 Fig. 11; v Fig. 13 is a topplan view of the core, of 'FigiJll,

and showing in dot-dash lines the slightly. projecting end portions ofthe two layers of rubbe which are bonded to. opposite faces of said coreto form the tread block of Fig. 12;

Fig. 14 is a top plan view of the core oi. each of the middle treadblocks of the track oi Figs.

rubber which are.

'lin es;'

and 2, the slightly projecting end portions of the rubber layers of suchblock being indicated in dot-dash lines; I r

Fig. 15 is a side elevational view of the core of Fig. .14, and showingin dot-dash lines the outer tread block. containing the core; ofzFi'gs.14andll)v 15, the view being in the plane of theline IB-l 6, Fig. 15;

Figs. 17 and 18. are detail views showing I slightly modified formoffastening meanszf sheet metal core members of the type show-11 iFigs-14, 15 and 16, the bottomtwo coremembgr of Figs. 15 and 16 havingtheir bolt-receiving apertures slightly enlarged to receive=theanchor-+ing portion of a lock nut-Fig. 17 being a VifiW.

partly in vertical transverse section and'partly' 20 coretd-formsa-idrtread .block'being indicated in in side elevation, and Fig:l8sbeingna:horizontal:

cross sectional'vievc.on thejline I 8+- tB; Fig. 17; i Fig; 19: is w anexplodeditypaof-view; showing in side elevation an .outer core memberandan inner core member, saidtwo -memberseconstituting one 2 Fig.- 22-is-a cross sectional view-pf'the:outer core member of 19; the-*view"being onthe line 22-22, Fig. 19; v

Fig. 23'isa crossflsectionalview of the inner core member ofFig. 19;ther viewbeing on'the line 2-3-23; Fi 1 1- Fig.24is'atopplan-view'ofatransversely split ,40'

form-ofcore for a correspondingly split; formofalternatemiddletreadblock;the projectingend'portions 'of'the' twosections of "rubber which such block' includes being indicatedindot-dash F,ig '25'is aisideelevationa-l;view=of the twosectionaljcoreof. Fig; 24; and-showing-in dot-dash lines .thebuter peripheries ofthe-two-sections of rubber in'whichsaid core sections are-embedded;

Fig-2,6 is angendelcvational view of one of the two "duplicate core'sectionsof the core 'of Figs! 24,and-25 and-thesection of rubber-inwhich said core section-is embedded; t Q

Fig. 27 is ,anexplodedf-type-of view, showing in" side elevation j threeof thefour sheet metal members of a-section'of the coi'e*of- Figs.'24 to26;

inclusive the fourth and other outer-member 'of saidcore' section, nothere: shown in Fig. 27, be-

ing identical with the outer coremember shown at'the top of thisview; I

Fig. 28 is a top plan view of the outermember 2 of Fig. 27; as;viewedfrom the line 28=-28,

Fig. 29'is -a' top plan -view of the adjacent "inner member of Fig. 27,as viewed from the line 29,29',, Fig. 27; the view 'also beingillustrative of the other-inner member of the'core section, inas Fig.32is a 'fragmentary view;' showing in side 75 elevation the frontendportion of -'a' somewhat modified form of core, in which the frontend flanges of the two inner core members are bent outwardly over thecorresponding flanges of I the two outer core members;

Fig. 33 is a similar view of another modified form of core whereinthefront .end flanges of the four inner and outer core members are maintained in assembled relation by a sheet metal n h.

Fig; 34 is ,a fragmentary view, showing in side elevation the front and"rear end portions of a modified form of four-piece core, wherein eachouter core member has one of its end flanges bent'over-the adjacent endflanges of the. other core members; v

35 is a .topplan view of a core'of a tread block which extends entirelyacross the endless track in'which-r it is used, the projecting frontand. rear, edge portions of the layers of rubber which are bonded to theopposite faces of said dot-dash; lines; I

Figs 36 is afront elevationalview of the core ofrFig; 35, with a ipartof=such core. broken away to show interior construction; the:outerperipheries of'the two layers of "rubberwhich are bondedtothe-opposite faces ;of: said'core-to, form a tread block being indicatedin dot-dash lines;

Fig. 37'is a: view'partly in vertical'sectionand partly in sideelevation lof'a treadblock contain-- ing-the core of Figs. 35 and 36,the view being on the line 37 31, Fig. 35;

Fig38 is=atop plan view of portions of "twov of i the tread blocks ofFigs. 35; as assembled in end le'sstrackrelation; Fig 39- is atop planview of "a modified form of core of a tread block of the'typewhichextends across-the endless trackin which it is used; theprojectingfront and ,rearportionsof'the layers of rubber which arebonded "to opposite faces of said "core toform said tread block-beingindicated indot-dash lines; v

1. Fig; 40 is a' view of the core of Fig. 39, partly in front elevationand partly in vertical section, on the line 40-40 of Fig. 39, the outerperipheries of the two layers of rubberwhich are'bonded'to I r is notlimited to the details of construction or the}- specific arrangement ofparts herein illustrated ordescribed, as: the "invention obviouslymaytake other forms. It'also'is to beunder'stood' that the vphraseologyor terminology herein em ployed is for purposes of description andnotoflimitation, the scopefof the present inventionbe- I ing indicated bythe-appendedclaims.

In'Figs. 1 and 2is;shown' a-sectionflof an endlesjs track whichcomprises three rows-of generally rectangular, longitudinally disposedrubber tread blocks, each containing a sheet metal core; em-' bodyingthe present invention, therebeing two laterally, spaced rows ofsidetread blocks ln and arow of middle tread blocks I Lthe middle treadblocks being staggered with respect-to: the side necting means forms nopart of the present invention. For the purpose of thisapplication, it issufficient to point out thattwo such cross rods extend through the endportions of a middle tread block and through the side tread block endportions'which overlap said middle block. As a result, and as anexamination of Fig. 1 will make evident, each middle tread block isconnected to four side tread blocks (two on each side thereof), and eachside tread block is connected to two middle tread blocks, inasmuch aseach side tread block is overlapped by the end portions of two middletread blocks. It may also be pointed out that the laterally projectingend portions 83 of the cross rods I2 not only carry the means whichconnect said rods in pairs but also carry parts which cooperate in thedriving'and guiding of the track. However, inasmuch as said driving andguiding parts are not involved in the present invention, they have notbeen illustrated and no further reference to them will be made.

Inasmuch as the side tread blocks of the track of Figs. 1 and 2 are ofidentical construction, a description of the sheet metal core of one ofsuch blocks will sufflce for all. Similarly, as the middle tread blocksH of said track are of identical construction, it will be necessary tode scribe the core of but one of those blocks, the cores of the side andmiddle tread blocks l0 and II differing somewhat, as will hereinaftermore fully appear.

Each of the tread blocks 10 and II includes, as indicated .in theaccompanying drawings, 'two layers of rubber between which the core islocated, said layers of rubber being bonded or caused to firmly adhereto the outer faces of the core. Usually, the ground-engaging layer ofrubber, herein designated by the reference numeral l4, has a somewhatgreater thickness than that of the other layer of rubber, hereindesignated by the reference numeral l5, as here shown.- Referring now tothe core which is used in each of the side tread blocks l0, it will benoted from an examinationlof Figs. 3 to 9 inclusive that said core ismade up of fours simple and inexpensive sheet metal members of generallyrectangular form in plan view, These four core members may, and here do,have the same width and length, and they are assembled in stackedrelation, one above another, in a unitary structure, with theirperipheries in alignment, as clearly shown in Figs. 4 and 5. Also asthere shown, the width and length of the assembled core memberssubstantially correspond to thewidth and length of the two layers ofrubber l4 and I5 which are suitably bonded to the outer faces of thecore, with the consequent re-enforcement of such layers of rubberthroughout their entire area. For manufacturing economyand simplicity ofassembly/the two outer core members l6 and I! (the top and bottom coremembers, as viewed in the drawings) are preferably identical andtherefore interchangeable. Similarly, the two inner core members l8 andI9 are preferably identical and thus interchangeable, although it is tobe understood that the sheet metal core for the side tread blocks Hlmaybe of the form in which no two members are duplicates. I

As best shown in Figs. 4 and 6, each of the two inner core members l8and I9 is provided adjacent each end thereof with a transverselydisposed semi-cylindrioal corrugation 20. As a result, when the twoinner core members are assembled in superposed relation, with'their cortransverse passageways 21 of cylindrical form are provided, one" for thereception of each ofthe two cross rods 12 which extend through each sidetread blocks. If desired, and as here shown, the

diameter of'the core passageways thusformed may be somewhate greaterthan that ofthe cross rods I I2, in order that such passageways maybeprovided with rubber linings 22 (see Fig. 2), although, obviously, saidpassageways may be made of such; size as to just receive said crossrods, as

' will be readilyunderstood;

, corrugations 20.

As here shown, welding is used to unite the two inner coremembers insuperposed relation, the character of the welding and the location ofthe welded areas being such as to securely and effectively unite saidmembers. Preferably, said inner core members are welded to each otheralong their overlapping end flanges 23, and along their overlappingmiddle portions between the ing of the two inner core members, the twoend flanges 23 of each such member are here proa Vided with transverselyspaced welding projections 24, and the middle portion of each suchweldingprojections of the'other, inasmuch as the two inner core membershere shownare of dupli. cate form, and to properlydistribute the weldedareas, each such inner core member has its two sets ofweldingprojectionsi24 suitably staggered,

' with a' corresponding staggering of its two sets of weldingprojections :25. As here shownfeach innercore member has one of its endflanges 23 provided with a row of two welding projections 24 and itsother end flange provided with a row of three Welding projections 24.Similarly, each' innercore member has two welding projections 25 in oneof its rows, and three welding projections 25 'in'its other row, all asclearly shown-in Fig. 8. Thetwo inner core members are so as-' sembledthat unlike end flanges are brought together, the two projection flangeof one'member lying opposite the three projection flange of the other.The transverse'spacing of the welding projections 24 and 25 ofueachinner core member is such that when said two core members arethusassembled, there isa'row of five transversely spaced weldingprojections 24 between each pair of end flanges 23 and two rows of fivetransversely spaced welding projections 25 between themiddle portions ofsuch core members;

. Thettype of welding preferably used for the uniting of the two innercore members is the well known resistance welding, the weldingprojeotions'24 and 25 being melted in .the weldingoperation by the heatcaused by the resistance of the electric current. Theqtwo inner. coremembers are thus united in a particularly effective and durable manner.

As indicated in Figs. 6 and 8, the welding projections 24 and 25 notonly are spaced across the entire widthof the inner core'members but-arelocated as close as possible to the corrugations 20 therebetween, theeffect of which is tomini U rugations oppositely disposed and matching,ltwo For the connection by'weld mizeany tendency of the, two innencoremembers to separate-or become disconnected evenunder severeconditions.of use; l

' Asabestqshownin .Fig. 4, the

two outer sheet metal'core'members lfiand li (the top and bottomv coremembers, as viewed-in Figs. 4 and are also provided adjacent their endflanges with transversely'dispo-sed corrugations of semi-cylindricaliform, the corrugations 21- of such ,outer core members fitting over thecorresponding co r,

nd':=the,=,-.outer:cor :m m e siare; hus-caused: o:

be rigidly and firmly united to; the twodnner corememberson'opposite'faccslithereofg Aszbest shown, in: Fig. -3, the"Welding projections 1 3,3 oi thegend flanges 32 of thegoutercore membersare not only staggered with-respectto1 thewelding rugationslllof the twoinner core members when gitudinal bridging of the two transversecorrugae tions ofeachof the outercore members, the layers of rubber l4and I5 are efiectively 'reenforced between the corrugations of-said coremembers, as will be readily understood. If de-.

' sired, and as here shown (see'Fig; 4), the top wall of the rib 2B ofeach outer core member-may be provided with a longitudinallydisposedchannel 29;which not only strengthens and rigidifies such coremember but also, aids in the anchoring. thereto of the appropriaterubber layer M'or IS.

The two outer core members-wand are each projections 24 of theend'flanges 23 of the inner core members but also, are; locatednearer-tothe aligned end edges of the two setsof flanges, namely, byadistance corresponding to the'thicm ness of {the metalof,whichthe,.outer core members are; made. l I v From, the foregoingdescription of the a core which is here used in -each of thesidetreadiblocks IUJ' Of the track-of-Figs; 1'and2-,:it:wi1l.beevident thatsaid core, 'of' sturdy-box-likeaform' in :cross section, is well adaptedto efiectively re-enforce the v,rubberlayers of .such block, andthusenable said block to successfully withstand the -=severe abusetowhich it is frequently: subjected in use; It will be equallyevidentthat the four sheet metal members which comprise said: core;although of relatively-light weight and-, capableof being easily andcheapl made; are so1c-onstruct ed asto give themgreatstrengthand'rigidity; so asto enable thetwo inner core members-atereceive thecross-rods I2 which extendatherethrough (thusmaking whollyunnecessary the use of seamless tubing and spacing strips therefor); andso asp-to enable; the layers .ofrubber to be efiectively anchored to theouter faces of the'outercoremembers, etc.;,,

provided, on opposite sides of its longitudinal rib 2B :and between itstransverse corrugations 21, with fiat-side edge portions 3|, whichcontactthe middle portions of the inner core members adjacent their sideedges when the two outer core membersware-assembled with the'two innercore members, on opposite faces thereof. As a result of the provision ofthe ribs 28, the core is of boxlike form in cross section (see-Fig; 5)andhence; one. which is of exceptionally strong and rugged character, aswill be readily understood. The

- provision of the ribs 28 of the outer core members also-is of materialassistance in the transverse anchoring to such core members of thelayers of rubber l4-and.l5, and inasmuch as the end portions ofsaidlayers of rubber extend around the corrugations 21 of saidcore memberstotthe end flanges 32i'the'reof, as clearly shown in Fig. 4, a

longitudinal anchoringaof the layers of rubber to suchcore members isalso effected. To bond or bring about a secure adherence of said layersof rubber to the outer faces of the'outer core members, any suitablemeans may be, utilized, such as the copper plating of such faces, forexample. Inasmuch as the outer core: members 16 and l1ihere-shown are ofduplicate form, no special care need be exercised in assembling-themwith the two inner.- core members on opposite faces thereof. To maintainsuch assembly, resistance welding is here utilized, and for thatpurpose, the

front and rear :flanges 32 of the outer core members; and the'flatgsideedge portions 3| thereof,

are provided with welding projections, there being four weldingprojections 33 spaced in a rowalongeach of the end flanges 32. and twowelding projections 34 spaced along each of the side'edge portions 3|.-In'the welding operation, the weldingxprojections 33 and 34 are meltedby the heatcausedbyttherresistance of the electric current;

If desired, howeventhe core of-the side tread blocks lltmay be, onewhich consists of but-two sheet metal members, suchas thecoreillustrated in Fig. 10. Inasmuch as the two duplicate members Iliavand |9a of the coreofFigclo are iden-- tical with, andare united instacked relation by welding in the same manneras; the two-dupli cateinner. coremembers l8-and l9 aofithe core illustrated in Figs; 3'tot-inclusive and-heretofore described, no further-descriptionof the corof Fig. 10 is believed to be necessary.- y I Another form of;two-'piececore which maybe used, in eachof thegside tread blocks-H], and which isof box-like-form in cross section, is -il lustrated:in Figs. 11 tol3,inclusive.- The-two duplicate sheet metal members36 and 3:1 of thicoreare substantially the-same'as the outer members l6 and-1 hot thecore of Figs.- 3 to, 9 inclusive.- It will'be noted, however;particularly from a comparison of Figs.- 12 and5, that thelongitudinalribs 38 of core members 36 and 31 are somewhat narrower than thecorresponding ribs- 28;

of coremembers l6, and IT, and thatthetopwalls of-ribs38arenot'channeled, although theyobviously may be, if desired. ,Italso willbe, noted that although the contacting-side edge portions 39 of the coremembers 36 and,31"are,-united.by;

welding, (for which purpose, each of saidiside, edge portions isprovided with ,a 'weldin IQIQ- jection 40); the front andrearend;flanges-:41: of such members are-connectedby bending; one of theend-flanges of each member over the-;ad-

jacentend flange of the othenmember; a: type;

of inter-lock whicheffectively-prevents; of course; endwise separationofsuchmembers; As to this form'of core, no;furtherdescription-isbelieved to be necessary.

Referringnow; to the core of eachof'themiddle tread blocksil of thetrackofFigsl' l and 2, it' will be'noted from an-examinationof'Figs;v 14-,15-and 16 and Figs; 19 to 23 ,inclusiveithat :such' core comprises-foursheet metal ',members;:,there being two inner members 42 and 43:01?duplicate,

form and two outer members 44 and 45 of dupli-' cate form. It also willbe noted that these four coremembers are each provided adjacent its endflanges with transverse, semi-cylindrical corrugations corresponding tothe corrugations of the 5 members of the core of Figs..3 to 9 inclusive,and that the two corrugations of each of the outer core members 44 and45 are bridged by a centrally disposed, longitudinally extending rib 46which differs from the ribs 28 of the aforesaid 10 core only in that itstop Wall is not channeled, although it obviously may be. Instead ofbeing flat, as are the middle portions of the inner members l8 and I9 ofthe aforesaid core, the middle portion of each of the inner core members42 and 43 is provided with a centrally disposed, longitudinallyextending rib 48 of semi-circular cross section (see Fig. 16). As bestshown in Figs. 15 and 19, the ends of the rib 48 of each inner coremember merge with the side walls of '20 block comprising a layer ofvrubber I5, an outer 2.30

form illustrated in'Figs. 17 and 18 may be used incore member 44 and aninner core member 42, and the outer or ground-engaging section of eachsuch block comprising a layer of rubber I4, an outer core member 45 andan inner core member 43. As will hereinafter appear, the two core 35 Asshown in Figs. 19, 20 and 22, the front and .40

rear end flanges of the outer core member 44, and the flat side edgeportions 5| thereof, are provided with welding projections 52 for thewelding of such core member to the inner core member 42 in a, rigidsub-assembly, the type of welding used being preferablyresistancewelding. In a similar manner, the outer core member 45 and the innercore member 43 are welded together in a rigidsub-assembly. By copperplating the outer faces of the outerucore members 5 44 and 45, or by theuse of any other suitable means, the layers of rubber I4 and I5 arebonded or caused to securely adhere to such core faces, thereby unitingeach core sub-assembly with its layer of rubber, as will be readilyunderstood. For releasably connecting the two core subassemblies andtheir respective layers of rubber, four bolts 53 are here utilized, twofor each set of end flanges, said flanges being provided, of course,with suitable apertures 54 for the reception of such bolts. As shown inFigs. 14 and 15, but more clearly in Figs. 1 and2, the recessed heads ofthe bolts 53 lie within suitable recesses 55 at the corners of the layerof rubber 15 of the inner block section, said recesses affordingconvenient covers 5! for said nuts and the projecting ends of saidbolts, said covers being of such cross sectional shape and size as toprevent the turning of the nuts therein. As best shown in Fig. 14, saidcovers are provided with transversely disposed,

connected to the outersurfaces ,of'the end flanges of the outercoremember, 4 5,said cover flanges,

if desired, being welded to the end flanges of said core member duringthe Welding operation by which such core memberiand the inner corememberg43 are rigidly united in a subassembly. If desired, and as hereshown, each of-the nuts 56 may be provided with a short treadedextension 59 of reduced size and of slightly elliptical shape,.thebinding'of the threads of such extension with those, of the bolt 53extending through said extension producing. suflicient resistance toprevent undesired unloosening of said bolt, as will be readilyunderstood. I

From the foregoing description of the longitudinally split core ofv thecorrespondingly split middle tread blocks, l I, it will be evident thatsuch core, of double box-like form in cross section, is well adapted foritsintended purpose. It also .will be evident that the simple andinexpensive sheet metal members of such core are of exceptionally strongand sturdyconstruction, and are unitedinto two rugged sub-assemblies,which are releasably connected in a particularly effective and durablemanner. Moreover, the longitudinally split form of the middle treadblocks ll enables them to be readily applied to and removed from anendless track in thefield, if and when necessary, as will be readilyunderstood.

If desired, nutsand sheetmetalcovers of the the releasable connectionofthe two core subassembliesjust described inplace of the nuts 56 andthe sheet metal covers 5l. If that is done,

the bolt-receiving apertures, 54 of the rigidly united end flanges ofthe core members 43 and 45 will have to be somewhat enlarged, in themanner shown in Fig. 17, for the reception of the inner tubularanchoring portion 60- of the lock nut-6| of Fig. 17. As there shown, theaperture 62 in the end flange of the inner core member for, the,

reception of the bolt 53a is somewhat larger than the bolt-receivingaperture 63 in the end flange of the outer core member, in order thatthe inner end of such nut anchoringportion may be peened or headed overthe flange of said outercorememe ber for the anchoring of such nut. Asbest shown in Fig. 18, the aperture 63 of thefend flange of the outercore member, and. that part of the nut anchoring portion which 1 extendsthrough :said aperture, are of non-circular form, the effect'of which isto prevent turning of the nut, as will be readily understood. Forbolt-locking purposes, thenutof Fig. 17 is here provided with a.threaded extension 65 corresponding to the extensions '59 of the nuts 56of Fig. 15. The sheet metal cover 66, forthe protection of theprojecting end of the .bolt 53a. from the layer of rubber in which it isto be located, is a simple cup-shaped member, having its upper endcrimped into an annular groove of the nut extension 65, as shown in Fig.17.

form of middle tread block containing a sheet metal core embodying thepresent invention.- As best shown in Figs. 24 and 25, this alternateform of middle tread block, including itssheetmetal core,is oftransversely split form, the two sections thereof being duplicates. andbeing',disposed (as shown in Figs. 24 and 25) in abutting relation whenin use. I a

As best shown in Fig. 25, this transversely split core comprises twoduplicate outer sheet metal core members 68 and 69, eachof two-pieceform, and two duplicate inner sheet metal corememoppositely extendingflanges 58 which are suitably bers 10 and II, each of two-piece form. Itwill be evident from a corrrparison of figs; 25" and-I5, Figsa26IS-endFigs- 3U and 22,- that the outer I core members 68- and G 9 ithe"same construction (except fortheir two-piece form)"=-as'thetwo outercore members and-45 0f the longitudinally split core heretoforedescribed. It also willb'eevident froma comparison of -Figs.-'-25) andl5, Figs.-26 and 16 and Fig's z'i and-'19, that'the two inner coremembers 'lfl and 1 I differ in construction from the-twoinner members42- and- '43 of said longitudinally' -split core on'l'yinthe characterof their centrally disposed, longitudinally extending ribs 12 (thetwopart form' of said innercore members I0 and H, of course, beingexcepted); Asbest shown in Figs. 25, 27 and 29, the-ends-of the ribs 1TZ-oftheinnefi CGre' membersand H do not merge intothe sidewallsoftheirtransverse corr'ug'ations' (askiothe 'hollow ribs 48 0f the innercore members-Hand) but terminate in spaced relation thereto; and--furthermore, i the width J of saidribs l2 is such that theirsidewalls; as well 'astheir top walls; engage'the corresponding walls ofthe ribs -1 3-of the'outer core members and 69.

For the rigid connection in stacked relation of v the four core "partsof '--each-,se'ctionof thistransversely split core, '----welding is hereutilized,. the welding being preferablymfthe resistance type. For theconnection of the two inner core parts part is 'providedalongfits-endflange with engaging op'posit e facesiofisaid tinnerccore: par-ts,

asishown; Y

' Forlthe formation of atread 'block'sectiomeach suchassembly ofcore'iparts has: suitably bonded alternate form of middle tread*block;it=will -be evident that such core, like those'heretofore:;described; is well suited for the effective re-enforcementof 1 such tread block. "Each: of a the: sheet metal members of saidcore, ='althoughtof simple and inexpensive construction and a ofrelatively light weight; possesses great 'strengtlrand rigidity, andwhen united to form atwo sectional core,

afford the type ohm-enforcement 'required for a: tread :blo'ck'of'thischaracter. "Inasmuch as the two cross rods 12 which extend." through:this

tread block (one'through eachblock section): are

twowel'ding projections 16 i and-across thespace 7 between itstransverse corrugation and the closed end of its rib portion 12 with twqwelding pro- -jec'tions l1. During the welding -"operation;- theseprojections are melted by the heat caused by the resistance yor theelectric current, with the consequent rigid connection of the two coreParts,

as mll-be'-"readi-ly understood. As -hereto'iore pointdoiltfitheinnercore members 10 and I I I5 are of duplica form, and-in' order toproperly distribute aiid -spa'ce the welded areas of -each connectedpair -'ofparts thereof, the two welding projections '16 along me o'f theend 'flange l :of each innercore' mem ber- 'ar staggeredwith respect tothe twowlding'prbjections l6 along the other efidflange' thereof LSimilarly, the two "welding projections ll-adjacent one of thetransverse corrugations df'each {inner core member are staggere'wi'tn're'sp'ect tothe' two 'welding proconnected; at their end portions1.3,:the' *ltwo block sections are tightly held together 'intheiabutting relationship-shown inFigsmZ. and 25, and any tendency ofablock section to turn: about its "cross rod is effectivelyresisted. l

Inasmuch as the c'ross rods l zfsmust'be' pushed endwise through thetransverse passageways of the two :sections of:' the transversely 1split tread 'je'tio'ns "adjacent the "other transverse corru gationthereof. Asa result,the two-inner core parts of ea'chcore section'are'rigidly unit'edby a of 'iour equally 's'pacedwe'l-ding"projectionsls andby a row' brrour equally "spaced' weldingprm 'cti'ohs1T, as"indi'cated'in"Fig."24 and as will be readily "understood. 1

Forthe c'onnectionto eachfpair of inner core parts, on jo'p'po'sit'e'faces thereof, or a pair of outer core partsfweidmg is here used."Forsu'chf pur- 'pose; each outer core'part is"'provided along" its endflange 18 With'Weldihg projections"!!! (five, 'as' here shown) andacross "the t'0pWal1 of "its ri'b' portion 73, 'adjac'ehtthe' "free edge80 thereof, with'weldi'ng projections? I "own; as here shown) Each suchcore part isalso'providedjwitha" welding projection B2jon each of'thetwo flatportions 83 thereof which lie on opposite sides ofits'longituglinal rib' portion 13,- as bestshown in'Figsy28 and 30. Bythe use of these weldingprojections '19, 8! and 82, which-melt by theheat caused by the resistance of the electric current in-the weldi-ngoperation; each pair of inner core parts has unitedtherewi-th; inarigid-and unitary-assembly, a pair of cutercoreparts, said outer 'core'parts block of Figs. 24 to 29 inclusive-and inasm uch as the endportions f of said cross rods -may, and

*40 preferably do; fit tightlyin thecorresponding passageways'of theside-tread blocks-'(thelatter passageways being rubber lined, ifdesired) ,replacement in the field of se'ctio'ns "of the treadi b'locksof'Figs. 244120 29 inclusive can best-be made:by the use -'of factory:assembled replacement-units.

Each such-*- unit will I' comprisei. a cormected pair of cross :rods 2Qn -Whi'chJare'. mounted two side tread blocks :and two middle t-read'block -sections, said sections" constituting;-when' Iin': a track, theadjacent sectionsliof- :two adjacent imiddle .-tread blo'cks. damagedone can be easily made in the field-wall as-will be readily-understood.

.31 In Figs. 32, -33wan'd 34 :are i1lustrated=modified arrangements forun'iting the end-flanges bf cores which comprise four core members. In"Figfl32, the contacting end -fian'ges -85 of the *two inner 'sheetmetal core --members are bent around the adjacent end flanges i of theouter core members. It is thus nec'essary to unite by-"weldingor othersuitable means only the end flanges of the: inner core memberstomaintainthe founcore -members in assembly; In 'Figfi33, the'endflanges ofrall 'four' core "members are'imaintained in stackedrelation by welding thereabout asheet metal locking'strip '86 ofchannel-shaped 'crossrsecti'on. In mgr-34,? thetwo duplicate outer'core:members 1 each has an assembly-maintaining end flange, the rear endflange 8] ;of -the outer core member -81abeing: bent" around; the rearend -flange:of;the outer core member BBa'andthe rear end'l-flan-gesofthe two inner core members; :and the frontend flange "8810f the outercorernember M r-being bent around the front end flanges-of theoutercoremember 81a and 'the front end The substitution of such a unit foraThe'core of'Figs. 35to 37 inclusive is therefore flanges'of the twoinner core members. With such a'connectionof theend flanges of thesefour core members, no welding or the like is neoes sary.

If desired, the end flanges of the core membersof the side tread blocksI 9 and the end flanges of the transversely split coremembers of thealternate form of middle tread block may be connected by any of thearrangements shown in Figs132, 33 and 34. The arrangement of Fig. 32(but not those of Figs. 33 and 34) is also suitable for the end flangesof the two core'sub-assemblies of the longitudinally split core of themiddle tread blocks I [if the connection of the end flanges of the twomiddle core members is eflected by bolts and nuts or other fasteningmeans of-the releasable or detachabletype, rather than bywelding,inasmuch as the two core subassemblies of the middle tread blocks llmust be capable of convenient separation, as heretofore pointedout. I InFigs. 35 to 37 inclusive is shown a tread block 90 which is transverselydisposed in the endless track in which it is used, the track-beingformed by a series of suchblocks arranged sideby side, as indicated inFig. 38, with each block having a length co -extensive with the width'ofthe track. Like the tread blocks heretofore described, the tread blocks90 also are adapted tohave extended therethrough suitable cross rods(not shown) by which they are maintainedin endless track'form, theprojecting end portions of said cross rods being connected in pairs bymeans not necessary to be here illustrated or described.

As best shown in Fig. 37, the layers of rubber l and M of the treadblock 90 are separated by a sheet metal core embodying thepresentinvention. As such view clearly shows, said core comprises six sheetmetal members, there being a pair of duplicate outer members, a pair ofduplicate inner members, and a pair of duplicate members 9| of generallychannel-shaped cross section, said channel core members being disner, asthe corresponding members of the core of v the side tread blocks Ill.The only structural dif-' ference therebetween is that each of the outermembers of the core of the tread blocks 90 isprovided withtwotransversely spacedchannels 94; rather than with a single channel (thechannel of each of the outer members of the core of the tread blocks [0being numeral 29). 1

As clearly shown in Figs. 36and 37, the oppositely extending flanges 92of the generally channel-shaped members 9| of the core of the treadblocks 90 are provided with suitable depressions 96 to receive thechannels 94 of the outer members of such core. It also will be notedfrom an examination of Fig. 35 that said outer core membersareprovidedwithwelding projections 91 for use in uniting to such membersthe flanges 92 of the channel coremembers 9|. From an examination ofFigs. 35 and 36, it will be noted thatthe channel core members! are ofslightly less length than that of their associated core members. i i i adesignated by the reiere'nce well suited for the re-enfo'rcement ofa'ftread block having a length coincident with the track I whichblockhas a length co-extensivewith the width of'suoh track.

The tread block 98, like thesother tread blocks heretofore described,contains a core embodying the "present invention. As best shown in Figs.39 e and 40, the core of this tread block'98 comprises four sheet metalmembers, there being apair of duplicate outer core members, and a pairof 'duplie cate inner core members. As will be evident from a comparisonof Figs. 41 and 37, the twoiinner members of the core ofthe tread block98 are of the same construction as the two inner members of the core ofthe tread blocks 90. It also will be evident from an examination ofFigs. 39, 40 and I 41, that the two outer membersof the core of thetread block 98 difier from the inner members of such core only by thetwo'laterally spaced ribs 99 with which such outer core members areprovided between their two corrugations. From an examination of Fig. 39,it will be evident that the four members of the core of the tread block98 are united by welding, the front and rear flanges of such coremembers, and thoseportions thereof lying between their corrugations,being provided with suitable welding projections for-such pur- I pose;As best shown in Fig. 40, the ribs 99 of the outer core members are ofgenerally semi-circular cross section.- When arranged in matching pairs,they form generally tubular re-enforcement parts which afford greatstrength against torsional stresses,-as will be readily understood.

No further description of the core of the tread block 98 is believed tobe necessary, although it may be pointed out that such core enables thelayers of rubber of such block to have material thickness (between thecorrugationsof such core) throughout substantially the entire length ofthe block. This produces substantial cushioning'efe feet b'etweenthecore corrugations, readily understood. Y

As heretofore pointed'out, the outer faces of as will be I the treadblock cores here illustrated and dc scribed may be, and here are, copperplated'to enable the rubber or the tread blocks to be bonded to suchcorefaces. Inthe copper plating of said core faces, which takes placeafter'the, cores. are formed, the use of several solutions is necessary,and in order to avoid any liability of the co-mirigling of suchsolutions, by the travel OfthQCOIBS from one solution to another, thefour 'member cores here illustrated are provided with suitable drainageapertures and/or drainage passageways, as Willhereinafter' ap-' pear. Nodrainage apertures or drainage pas;

sageways are necessary in thetwo member cores here illustrated (the coreof Fig. 10 and the core of Figs. 11- to 13 inclusive), inasmuch as frombefore they rcach the next solution into though either :such aperturesor such tpassageunited with the two inner core 'members -liil and I9) toreadilydrain into the open e'nded transverse passageways 2 I 'formedbythe' corrugations 20 of the inner-coreymembers. The draini-passagewaysof this core are formed the flat side portions 3| of the outer=coremembers46 and I1, there being: one such drainage :passagew'ay ineach=such portion :31, as clearly-showndn 3 'and 7i Inasmuchas thesedrainage passageways-IOI communicate at their innerends with the-hollowsof the ribs-2 8 of :theouter core members, and areo-pen at their outererids, anysolution in/the hollows-of such ribs will readil-y draintherefrom through-suchflpassageways; As here tofore pointed out, the useof both-the drainage apertures I and the drainage passageways 41H arenot necessary, although thezuse-of both en? ables the core to bereadilydrained. in any: posirtion in which it is suspended during its travelfrom one solution to the next as will bereadily understood.

As will be evident from-an-examina-tionofFigs;

14, andflG and Figs. 1 9 -to;-23inclusive-the longitudinally split coreof -the middle tread blocks 'II is provided with dr'ainage apertures I62and drainage passagewayslila't identical with those ofthe core of theside tread blocks 40. a result, no further reference to the drainageapertures and the drainage passageways ofsth'e, core of themiddle tread.blocks H-isneeessary;

"In the transversely split core of the alternate form of middle treadblock illustrated in Figs. 24

to '29 inclusive; a drainageapertureIM is provided in the transverse.corrugation of r each part of the'two inner core members 10 --and "H. Asbest shown 'in such apertures communicate with the ends of thehollow-ribs 13' of-theouter core members '68 and "69 and thus-permit anysolution in the hollows of said ribsto be drained therefrom. Ifdesired'and as here shown, the

top wallo'f the rib "I2 of each of the inner core memb'ers may beprovided with a drainage spas sageway I65, the provision of thepassageways establishing communication between. thosepore ti'ons ofthehollow of each rib 'I 3.--wl 1ic hlie on opposite sides. of the rib 12therein, as- ,-wi1lbe evidentfrom an examination of Fig. -2 5 In thecore of the tread block 90' of Figs. 35- to 37 inclusive, th'reedrainage apertures liliirare provided in each of the corrugations of theinner core members for the drainage of the hollows of the channeledribsof the outer'core members;

Drainage passages IIJ'I- also-may be .provided, if

desired and as here shown, in the base portions I108 oifthe generallychannel-shaped-core mem bers B I, the result of. which is to eestablishcom afar-1:157: I

' draining the'ribs 9 9" of j: the oute'r core membersl If: desired;and-as hereshovvn; drainage apertures I III-also may 'beeprovidedin: theouter core I members, between their corrugations,. to permit the escapeof "any solutionswhich maiy find-' its way between those portions of imeinner core mem bers :which lie b'et-wee'n their corrugations andcon'esponding por ions'ofthen-outer core members.- I a on heretoforepointed'outf: the outer members I6 and of the core 'of Figs;.3to"9inclusive=have their front and r rear flanges 32 'spot welded tothe corresponding flanges 2-3of the inner i'nembers I 8 aud t-90f saidcore. =In-order to supplementthespot-welds which thus unite sa idfianges,

the -corrug-a-tions "21 of the --outer core m'embers I 6- and I I maybe, and here aregsuitably brazed to the correspondingcorrugations of ythe, Y inner core members I8-= and +8. For purposes 5 ofsuch brazing;the outer: corrugations L l/are -.provid ed .with suitable apertures IIIprovidingyaccess to the inner corrugations 2 U and: receiving more 701less of the brass or spelter -I|-2 utilized in the braaing -operation,said' apertures being located, preferably, as close as possible to; the"front and rear flanges 3-2 oi the outer core, members.

v though the number ofapertures III with which to enable them to bespaced along the fulllen-gtheach corrugation 21 is providedmaybesuch==as of said corrugation,- each such corrugation -2-'I isliere-provided with four such-apertures, two-adjacent each end ofsaidcorrugation, as H clearly shown in Eigsr3- and 7. i I

Also, if desired and as here showm the spot welds by which are unitedthe two front flanges 23 "ancLthe two rear flanges '23 o-f the inner members I8 and I 9=of the oorepiFigs. 3 -to -9;incl-usive may' besupplemented by further welding rot-such flangeasuch as -at the rearedges of the front.- pair of flangesand at thefrontedges of the rearpair pt fiangesas clearly-shownat I I 3 in' -Figs.- 3,. v '4uand'6.Such"additionalwelding; of- -ei-therthe ga or arc type, may extend the'full -lengthof suchfflan ges or, if desired -onlyt along the endportionsthereof, as will be readily understood.

Supplemental welding like that-designated by the reference numeral-J43may alsobe used, if

desired, in connection with the two members'of the 'core of Fig. 10, andin connection with the inner mem-bersof the cores of Figs. '24 I to #29i'rr-s clusive, l ig.-32, Figs. Eto 138 inGluSiVe 13Ilfd*FigSm 39- to-4-1. inclusive. Similarly; the outer member's or the-cores of Figs. 24'to' 29 inclusive, 'Figs..-35:

to 38 inclusive and Figs. 39120-41 inclusive may be provided with:apertures, likethosede'signated by theareferenee numeral-- H-I inorderthatsuch:

outer core members may berbrazed'to :the: inner: core members 7 withiwhich "they iiare associated,

' all aswill be readily-understood;

e'nt invention will be readily apparen't't'o those skilled in the art to'whichi t relates; M hatl'claim isz:

"1 A core -for'the 'rubber tread blo'ck-6 :dmend less- -trackoftliefitype' in which the tree of suchtrackehavecross iods extendi n teray therethrough;.said core comprisingenpan f sh et metal member's'rig'idlyconnected instacldd rela munication between those portionsoffthe-hOllow ofv each rib or the-outer ooremembers which are disposedon opposite-sides of the core member 91 therein.

In the tread block core of Figs. '39 to 4 1 inelusive, drainageapertures- 409 are-:prov idedi irr-the corrugations of. the inner coremembers for extending and lateral disposed tion. I nd: provided.adjacent" each df tlie 'frb'nt andsrearr edgesath'ereofl wi-th a pa -foppositely rugations coextensive-- Further .-f;eatures and advantages 1of. the pres w re 'tbhir'ig corith the length ofsiibh" edges;iea'chep'air of? such sms-toning eonugatiens providing;Earl-laterallydisposed 'eassag'eway be tween said core members for a correspondinglydisposed track cross rod, the two passageways being in generallyparallel relationship, the front passageway being closed along its frontside and the rear passageway being 'closed along its rear side, the twocore member between the front and rear passageways being substantiallyin abutting relationship.

2. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal members rigidlyconnected in stacked relation and provided with overlapping flanges ateach of the front and rear edges thereof, said pair of connected coremembers also being provided adjacent. the overlapping flanges at each ofthe front and rear edges thereof with a pair of oppositely extendingmatching corrugations coextensive with the length of such edges, eachpair of such matching corrugations providing a passageway between saidcore members for a track cross rod.

3. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal membersarranged in stacked relation and provided at the front and rear edgesthereof with rigidly connected overlapping flanges, said pair ofconnected core members also being provided adjacent the overlappingflanges at each of the front and rear edges thereof with apair ofoppositely extending matching corrugations coextensive with the lengthof such edges, each pair of such matching corrugations providing a passageway between said core members for a track cross rod.

4. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal membersarranged in stacked relation and provided adjacent each of the front andrear edges thereof with a pair of oppositely extending matchingcorrugations coextensive with the length of such edges, each pair ofsuch matching corrugations roviding a passageway between said coremembers for a track cross rod, said coremembers being rigidly, connectedby the connection of those portions of each member lying on oppositesides of each of the corrugations thereof to the corresponding portionsof the other member.

5. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal members rigidlyconnected in stacked re lation and provided in the region of each of thefront and rear edges there-of with a pair of oppositely extendingmatching corrugations coextensive with the length of such edges, eachpair of such matching corrugations providing a passageway between saidcore members for a track cross rod, at least one of said core membersbeing provided with a strengthening rib extending betweenandsubstantially normal to the corrugations thereof.

6. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal members rigidlyconnected in stacked relation and provided in the region of each of thefront and rear edges-thereof with a pair of oppositely extendingmatching corrugations coextensive with the length of such edges, eachpair of such matching corrugations providing a passageway between saidcore members for a. track cross rod, said core members also beingprovided between and substantially normal to the two pairs ofcorrugations thereof with a pair of, oppositely extending matching ribs.

'7. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal members rigidlyconnected in stacked relation and provided in the region of each of thefront and rear edgesthereof with a pair of oppositely extending matchingcorrugations coextensive with the length of such edges, each pair ofsuch matching corrugations providing a passageway between said coremembers for a track cross rod, at least one ofsaid core members beingprovided with a strengthening rib extending substantially normal to thetwo corrugations thereof and having its ends merging with the side wallsof such corrugations.

8. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal membersarranged in stacked relation and provided with flange portions at eachof the front and rear edges thereof, said pair of core members alsobeing provided adjacent the flange portions at each of the front andrear edges thereof with a pair of oppositely extending matchingcorrugations coextensive with the length of such edges, each pair ofsuch matching corrugations providing a passageway between said core.members for a track crossrod, thefront and rear flange portions ofeach-of said core members, and the side edge portions thereof betweenits corrugations, being in contacting relationship with and beingrigidly connected to the corresponding flange and side edge portions of,the other core member.

9. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of inner sheet metal coremembers rigidly connected in stacked relation and provided in the regionof each of the front and rear edges thereof with a pair of oppositelyextending matching corrugae tions coextensive with the length. of suchedges, each pair of such matching corrugations providing a passagewaybetween said inner coremembers for a track cross rod, and'a pair ofouter sheet metal core members rigidly connected with said inner coremembers and disposed on op-' posite faces thereof.

0. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rodsextendingtherethrough, said core comprising a pair of innersheet metal coremembers rigidly connected in stacked relation and provided in the regionof each of the front and rear edges thereof with a pair of oppositelyextending matching corrugations coextensive with the length of suchedges, each pair of such matching corrugations providing a passagewaybetween said inner core members for a track cross rod, and a pair ofouter sheet metal core members rigidly connected with said inner coremembers and disposedon opposite faces thereof, one of said outer coremembers being provided with a strengthening rib extending substantiallynormal to the cor rugations of said inner core members.

11. A core for the rubber tread block or an endless track of the type inwhich the tread locks of such track have-cross rods extendingtherethrough, said core comprising a pair of inner sheet metal coremembers-rigidly connected in stacked-relation and provided in the regionof each of the front and rear edges thereof with a pair of oppositelyextending matching corrugations coextensive with the length of suchedges, each pair of such matching corrugations providing a passagewaybetween said inner core members for a track cross rod, and a pair ofouter sheet metal core members rigidly connected with said inner core'members and disposed on opposite faces thereof, one of said outer coremembers being provided in spaced relation to its side edges with astrengthening rib extending substantially normalto the corrugations ofsaid inner core members. 12. A core for the rubber tread block of anendless track of the type in which the tread blocks of such track havecross rods extending therethrough, said core comprising "a pair of innersheet metal core members'rigidly connected in stacked relation andprovided with spaced pairs'of oppositely extending matching corrugations extending generally parallel withthe front and rear edges of suchcore members and coextensive with the length of'suchedges, each a pairof such matching corrugations providing a endlesstrack of' the type inwhich the tread blocks of such track have cross'rods extendingtherethrough, said core comprising a pair of inner sheet metal coremembers rigidlyconnected instacked relation and provided with overlapping fiangesat each of the front and rear edges thereohsaid pair ofinner coremembers also being provided adjacent the fia'ngesat each ofthe front and rear edges-thereof with a pair of oppositely extendingmatchingcorrugations coextensive with the length'of such edges, eachpair of such matchingv corrugations providing a passageway between saidinner core members for a track cross rod, and a pair of outer sheetmetal core members rigidly connected-With said inner core members anddisposed on-opposite faces thereof, said 'outer'core members beingprovided at their front and rear edges withiflanges contacting theflanges of said inner core members and'also being provided withstrengthening ribs extending generally normal to-the corrugations ofsaid inner core members,

14..A core for the rubber: tread block of i an endle'sstrack-of thetypein which the tread blocks ofrsuch tracli have cross rods extendingtherethrough, said core comprising a pair of inner. sheetmetal core"members rigidly connected sheet metal core members rigidly connectedwith instacked relation-andprovided in the region said inner coremembers and disposed on opposite faces thereof, said outer'core membersbeing provided with strengthening ribs extending generally normal to thecorrugations of said inner core members, the top wall of at least one ofsaid ribs being longitudinally channeled.

15. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal core membersrigidly connected in stacked relation and provided in the region of eachof the front and rear edges thereof with a pair of oppositely extendingmatching corrugations coextensive with the length of such edges, eachpair of such matching corrugations providing a passageway between saidcore members for a track cross rod, and a supplemental sheet metal coremember rigidly Connected in stacked relation with said first mentionedcore members, said supplemental core member being provided with astrengthening rib extending generally normal to the corrugations of saidfirst mentioned core members.

16. A core for the rubber tread block of an endless track of the type inwhich the tread blocks of such track have cross rods extendingtherethrough, said core comprising a pair of sheet metal core memberrigidly connected in stacked relation and provided in the region of eachof thefront and rear edges thereof with apair of oppositely extendingmatching corrugation coextensive with the length of such edges, eachpairof such matching corrugations providing a passageway between said coremembers for a track cross rod, and a supplemental sheet metal coremember rigidly connected in stacked relation with said first mentionedcore members, said supplemental core member andoneof said firstmentioned core members being each provided with a strengthening ribextending generally normal to the aforesaid corrugations.

' 17. A core for the rubber treadv block of an endless track of the typein whichrthe tread blocks of such track have cross rods extending therethrough, said corecomprisingawpairvof sheet metal core membersrigidly'connectedin stacked relation and provided in the region ofeach-of the front and rear edges thereof with a pair of oppositelyextending matching corrugations coextensive with the-length of suchedges, each pair of such matching corrugations providing a passagewaybetween said core members for a track cross rod, and a supplementalsheet metal core member rigidly connected in stacked relation with saidfirst mentioned core members, said supplemental core member beingprovided with a strengthening rib extending generally normal to theaforesaid corrugations and one of said first mentioned core membersbeing provided with a correspondingly extending strengthening ribdisposed within the rib of said supplemental core member. 1 v

18. A core for the rubber tread block of an endless track of the type inwhich the tread. blocks of such track have cross rod extendingtherethrough, said core comprising a pair of sheet metal core membersrigidly connected in stacked relation and provided in the region of eachof the front and rearv edges thereof with 'a'pair of oppositelyextending matching corrugations coextensive with the length of suchedges, each pair of such matching corrugations providing a passagewaybetween said core members for a track

